In the previously known ink systems for ink jet matrix printers, the transport device has mechanically functioning pumps, e.g. membrane pumps or toothed wheel pumps. In some ink jet matrix printers, at least one mechanically functioning transport pump is used, by means of which the ink is transported from the ink chamber to the write head, and in addition, at least one suction pump is provided, by means of which droplets that have not been diverted for writing purposes are returned from the collection channel into the ink chamber. However, there are also ink systems which function with only one mechanically functioning pump, e.g. a membrane pump, whereby this sole pump generates pressure (in one direction) as well as negative pressure (in the other working direction).
However, the previously known ink systems equipped with mechanically functioning pumps have the disadvantage that the pump will eventually be worn down, i.e. that maintenance is required. In a mechanical pump, the moving parts as well as the sealing parts will eventually be worn out, so that disturbance-free operation is not possible for longer periods of time. In addition, the costs for such mechanical pumps is significant, which is noticeably reflected in the price of the ink system. Finally, problems will occur in mechanically functioning pumps when pigmented inks are used. For instance, if one should want to use white inks, one is forced to work with pigmented inks. Pigmented inks are mixtures consisting of two materials, namely small color particles and a liquid which does not constitute a solvent for the small color particles. In mechanical pumps, the small pigment particles of the pigmented inks will, over the long run, clog areas of the pump, so that its mechanical function is eventually disturbed thereby. A cleaning is extremely complicated and always requires a great amount of work.
Ink jet matrix printers are known in principle, e.g. from the German Disclosure Document 23 44 453 or the old US Patent 3 596 275.